1. Field of the Invention
This invention relates to a method for detecting hydrocarbons in soil, and in particular to a method comprising extracting the hydrocarbons from the soil using a water miscible solvent.
It is now well accepted that corporations and individuals have a legal duty to protect the environment, including soil, against contamination by the inadvertent release of oil or other hydrocarbons, and that remedial measures must be taken should such accidents occur. Various tests have been developed to enable investigators to detect the presence of hydrocarbons in soil to help identify sites of releases from leaking storage tanks and other sources of contamination. Other tests for hydrocarbons in soil have been developed for the mining industry to help locate drilling sites for petroleum recovery.
2. Related Art
U.S. Pat. No. 2,431,487 to Larsen, dated Nov. 25, 1947, discloses a method for detecting oil in drilling mud. The method involves mixing mud with a solvent for the oil which is miscible with water, to extract the oil into the solvent. A water-miscible solvent is used so that the solvent can penetrate the aqueous phase within which the oil resides in the mud, so that the solvent has immediate contact with the oil and a single phase within which the oil resides is created (see column 3, lines 24 through 34). A broad range of solvents is identified for use in the process, including ketones, alcohols, glycols and the like (see column 2, lines 7 through 16). Before adding the solvent, the mud may be diluted with water. Alternatively, the solvent may be mixed with water before it is added to the mud (see column 5, lines 34 through 38). After extracting the oil, the solvent is examined by exposure to ultraviolet light, and if the solvent fluoresces, oil is said to be present therein. Other analytical methods may be used to detect the oil, e.g., infrared adsorption, spectrophotometric analysis and the like (see column 3, line 72 through column 4, line 19). To better observe fluorescence, Larsen teaches a preference for a clear solution (see column 3, lines 50 through 54).
Mahendra Patel, in an article entitled Rapid and Convenient Laboratory Method for the Extraction and Subsequent Spectrophotometric Determination of Bitumen Content in Bituminous Sands, published in 46 Analytical Chem., No. 6, May 1974, discloses a method for determining the quantity of bitumen in sand. A sample of the sand is washed with an extraction solvent (toluene) to extract the bitumen from the sand. The solvent is subjected to photometric analysis, and the measured absorbance is compared against a calibration curve produced by analyzing a known test solution.